Question about changing automatic trans fluid

[BrentK]

I'm going to drain the (original factory) ATF from my 2000 Toyota Sienna, and replace it with Mobil 1 ATF. Since the existing fluid will have around 51,000 miles on it (and will have Auto-Rx in it) when I drain it, I'd like to drain/refill it again soon after the first drain/refill to remove as much of the old fluid as I can.

So my question is, how long (or how many miles) does it take for ATF to run through the entire system? Also, assuming that two drain/fill cycles isn't enough to remove enough of the old fluid, how many cycles are enough?


Brent

 

[FL-400S]

I think the general rule is that you replace 1/3 of the tranny fluid with each drain and fill. The fluid should fully circulate if you just let it idle for a minute or two. But Id probably drive it a few miles or even for a week then change it again. I wouldnt worry about doing 5 changes just to get every last drop of old fluid out. Its probably worn but not toast, so it should be fine. If it were me, Id just do 2 drain and fills. Then do one about every 10-15K miles. I did one on my tundra at 12K and plan to keep changing out 1/3 every 10-15 K miles.

 

[TR3-2001SE]

Honda recomends a change of the fluid every 30,000 miles. A change in this case is about 1/2 of the total. I would think two changes at 50,000 miles should give you the protection you are after.

 

[gfcrane]

I changed the fluid in my Maxima AT by this "drain and fill" method. It hold 9 qts and each drain gets 4 qts out. I did it three times (12 qts Chevron Dexron III). According to my spreadsheet calculations, this got about 82% new fluid in total. You can never get to 100% this way due to mixing and I figured this was close enough. Besides, I bought a 12 qt case for the job anyhow.